Update HTTPHeaderMap wrappers to use AtomicString type for header values

Source/platform/network/HTTPRequest.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 63 matching lines @@
     size_t result = parseHTTPRequestLine(data, length, failureReason, m_requestMethod, url, m_httpVersion);
     m_url = KURL(KURL(), url);
     return result;
 }
 
 size_t HTTPRequest::parseHeaders(const char* data, size_t length, String& failureReason)
 {
     const char* p = data;
     const char* end = data + length;
     AtomicString name;
-    String value;
+    AtomicString value;
     for (; p < data + length; p++) {
         size_t consumedLength = parseHTTPHeader(p, end - p, failureReason, name, value);
         if (!consumedLength)
             return 0;
         p += consumedLength;
         if (name.isEmpty())
             break;
         m_headerFields.add(name, value);
     }
     return p - data;
@@ skipping 14 matching lines @@
     , m_httpVersion(version)
     , m_requestMethod(requestMethod)
 {
 }
 
 HTTPRequest::~HTTPRequest()
 {
 }
 
 } // namespace WebCore